McIntosh MC901's internal active crossover & speaker's internal passive crossover

If you connect both MC901 outputs to a biwired speaker, you'll blow the amp.

Usually not.  Sometimes yes. Depends on exactly how the speaker inputs were wired and whether or not your amp outs are balanced or not.

A properly wired speaker for bi-wiring separates out the crossover sections entirely internally.  Some however short the grounds together, by design or by oversight.

It is not ideal to use both an active and passive crossover, but it is still workable.

erik_squires

A properly wired speaker for bi-wiring separates out the crossover sections entirely internally.

This is mistaken. What you have described is a speaker designed for biamplification. Biamplifying and biwiring are two different things.

If you connect both outputs of a Mac901 amplifier to a speaker not intended for biamplfication, you’re going to have problems. Big time.

I own these amps, and they are all you think they would be. Extremely versatile and easy to work with. When I purchased them, I ran Infinity IRS Betas. The mid/high panels with the tube section, and the bass towers with the solid state. I did not use the internal crossover since the Betas have a servo box for the Woofers and adjustable level crossovers on the mid/high panels. These amps sounded much better than a half a dozen or more previous arrangements with the Betas.

Now they are running a set of Analysis Audio Orion Mid/High panels using the internal crossover on the amps, with no passive crossover in line to the speakers. This is the best way to run these amps and sounds incredible. Another option is to run the monos as two separate amps for two separate types of speakers if you’d like to change up your flavor. You can run a more sensitive pair of speakers off of the tube section, and drive more power-hungry speakers with the solid-state section switching between based on your mood, but this will need two outputs from your preamp.

Can’t say enough good about the MC901’s. I watch the used market daily and have yet to see a used set for sale since their introduction.

@cleeds 

What exacy do you think a speaker made for bi wiring does?  What do you think happens when you remove the external jumpers?

A biwirable speaker provides a separate path for lo and hi frequencies, but they are still joined electrically at the xover. A biamplified speaker provides electrically isolated paths for the two frequency bands. That's the difference between the two.